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Heat Transfer Module

New App: Finned Pipe Designer

Finned pipes are used for coolers, heaters, or heat exchangers to increase heat transfer. They come in different sizes and designs depending on the application and requirements.

When the fins are placed outside the pipe, they increase the heat exchange surface of the pipe so that a cooling or heating external fluid can exchange heat more efficiently. When placed inside the pipe, it is the inner fluid that benefits from an increased heat exchange surface. Instead of fins, grooves can also increase the heat exchange surface, particularly inside the pipe where space is limited.

With the Finned Pipe Designer app, you can customize a long cylindrical pipe with predefined inner and outer fins or grooves to observe and evaluate their cooling effects. The app calculates the thermal performance of a pipe that is filled with water and then cooled or heated by surrounding air with forced convection.

Various geometric configurations are available for the outer structure (disk-stacked blades, circular grooves, helical blades, helical grooves, or none) and for the inner structure (straight grooves or none).

The app computes the dissipated power and the pressure drop as functions of the geometry and air velocity.

New App: Thermoelectric Cooler

Thermoelectric coolers are widely used for electronics cooling in various application areas, ranging from consumer products to spacecraft design. Exploiting the Peltier effect, they consist of several thermoelectric legs sandwiched between two thermally conductive plates, one cold and one hot. Due the variety of applications, there can be many different thermoelectric cooler configurations.

The Thermoelectric Cooler app covers the basic design of a single-stage thermoelectric cooler of different sizes with different thermocouple sizes and distributions. You can use the app to help find the best thermoelectric cooler for a specific application. Manufacturers can also use it to optimize designs and provide application-related performance values. Additionally, the app serves as a starting point for more detailed calculations with additional input options and can be extended to multistage thermoelectric coolers.

This is done by varying the geometric parameters of the different components of the thermoelectric cooler, the material that makes up the thermoelectric legs, and some operating conditions.

User interface for the Thermoelectric Cooler app, with settings for the design, materials, and operating conditions.

User interface for the Thermoelectric Cooler app, with settings for the design, materials, and operating conditions.

New App: Measuring Thermal Conductivity Through the Flash Method

The flash method is widely used for measuring the thermal conductivity of a thin sample material that is about the size of a coin. The sample material is submitted to a laser pulse on one of its faces. In turn, the opposite face is heated up by around 1 K. As the pulse is uniform and well defined, you can measure the temperature variation on the other side. Thereby, you can measure the thermal conductivity of the sample with high accuracy.

The Flash Method simulation app reproduces the real-world experiment and provides options to define experiment parameters that can affect the accuracy of the method and your experiment. This means that you can specify sample height, radius, and material. You can also set the ambient temperature, enable or disable convection and radiation effects, and customize the values of the heat transfer coefficient and the surface emissivities of both the sample and the enclosure.

The app's user interface, showing the flash method's settings and the temperature profile used to determine the thermal conductivity.

The app's user interface, showing the flash method's settings and the temperature profile used to determine the thermal conductivity.

Symmetry Plane for Surface-to-Surface Radiation

A new feature with COMSOL Multiphysics version 5.2 incorporates a symmetry plane in a heat transfer simulation with surface-to-surface radiation in 2D, 2D axisymmetric, and 3D geometries. In applicable cases, this makes it possible to represent only half of the geometry, resulting in a view factor computation that is twice as fast. In addition, the number of mesh elements required is reduced to half for all dependent variables.

External Temperature for Thin Layers

The External Temperature subfeature is available under the Thin Layer feature when the layer type is set to Resistive or General. Applicable to exterior boundaries, this functionality enables you to specify the temperature on the exterior side of the layer, whereas the model determines the temperature in the layer and on its inner face.

Additional Correlations for Heat Transfer Coefficients

The heat transfer coefficients library has a new convective heat transfer coefficient correlation for natural convection around a vertical thin cylinder. This heat transfer coefficient lets you replace a nonisothermal flow simulation with a heat flux boundary condition on the cylinder boundaries to reduce the computational cost of the simulation.

New Subfeatures for the Thin Film and Fracture Features

A set of four new subfeatures extends the modeling capabilities available for the Thin Film and Fracture features. These subfeatures are analogous to those already available for the Thin Layer feature:

The Temperature subfeature

Used to specify the temperature on a set of edges that represent thin boundaries of a thin film or fracture. This condition is needed when the thin film or fracture inlet is on an exterior edge.

The Line Heat Flux subfeature

Defines a heat flux across boundaries of a thin film or fracture. The user interface provides different options for the definition of the flux: General inward heat flux; Inward heat flux; and for 3D models, Overall heat transfer rate.

The Surface-to-Ambient Radiation subfeature

Defines surface-to-ambient radiation on a set of edges that represent the thin boundaries of a thin film or fracture. The user interface provides inputs for the ambient temperature and surface emissivity, which are used for the definition of the net inward heat flux.

The Source subfeature

Defines an internal heat source within a thin film or fracture. This subfeature provides two options for the definition of the heat source: General Source and Overall heat transfer rate.

Updated Solver Settings for Heat Transfer

The default solver settings for the Heat Transfer interfaces have been updated. SOR is used instead of SOR Line as the presmoother in the multigrid solver for large models, unless the model contains a Non-Isothermal Flow coupling node. This leads to shorter computational time. In addition, a lower temperature limit of zero has been added for situations when a segregated solver is used, provided that the temperature unit is set to Kelvin.

Updated Heat Transfer Documentation

The Heat Transfer Module documentation has been fully revised for better clarity and consistency in COMSOL Multiphysics version 5.2. The new structure of the documentation contains several additional parts. In particular, new sections of documentation describe the default solvers generated for the Heat Transfer interfaces and the temperature variables available on boundaries.